Pitch determination using low time resolution input signals

Abstract

A pitch determination device which separates at least each frame of the input speech signal into separate, lower resolution portions is provided. The pitch determination device includes a resolution lowering unit, a signal selecting unit and a pitch determination device. The resolution lowering unit has an input line on which the input speech signal is provided and K output lines, on each of which output lines, one of K lower resolution input signals is provided. The signal selecting unit has K input lines connected to the K output lines of the resolution lowering unit and has an output line on which is provided one of the K lower resolution signals which fulfill a predetermined quality criterion. The criterion is typically based on the energy content of the lower resolution signals. The pitch determination device has an input line connected to the output line of the signal selecting unit and an output line which provides a pitch value for the selected lower resolution input signal. The lower resolution signals are subsampled by K, where each ith lower resolution signal is offset from said input signal by i sample points, where i varies from 0 to K-1. The pitch determination is performed by cross-correlating or autocorrelating between two low resolution signals, that of the input signal and of a shifted and offset lower resolution signal. For cross-correlation, the shifted lower resolution signal is a previously received signal. For autocorrelation, the shifted lower resolution signal is a shifted version of the low resolution input signal.